1. Field of the Invention
The present invention relates to a light scanning apparatus, and an image forming apparatus including the light scanning apparatus.
2. Description of the Related Art
Hitherto, an electrophotographic image forming apparatus includes a light scanning apparatus configured to scan a uniformly charged surface of a photosensitive member (hereinafter referred to as a “photosensitive drum” for convenience) with a light beam modulated in accordance with image information, to form a latent image on the surface of the photosensitive drum. The latent image formed on the photosensitive drum is developed into a toner image with developer (toner). Then, the toner image on the photosensitive drum is transferred and fixed to a recording medium. In this manner, an image is formed on the recording medium.
The light scanning apparatus includes a semiconductor laser (light source), a rotary polygon mirror (deflection member) configured to deflect a light beam emitted from the semiconductor laser, and a motor (drive device) configured to rotate the rotary polygon mirror. The light scanning apparatus further includes optical components such as an fθ lens (imaging optical member) configured to image the light beam onto a surface to be scanned, and a reflecting mirror (turning mirror) configured to change a direction of the light beam toward the surface to be scanned. In general, those components are arranged in a housing referred to as an optical box with high accuracy. FIG. 8A is a schematic structural view illustrating a generally-used optical component holding structure, and FIG. 8B is a cross-sectional view passing through a center portion of a leaf spring. A reflecting mirror 62 serving as an optical component is held and fixed to a housing 85 due to a pressurizing force of a leaf spring 702 serving as a pressing member. From the viewpoint of installation space saving and workability, the leaf spring 702 is put on an engaging portion 703 formed in the housing 85 instead of being fixed by screws. In the vicinity of the engaging portion 703, the housing 85 receives a part of a reaction force generated when the optical component is pressed, and thus the leaf spring 702 maintains a predetermined position. As illustrated in FIG. 8B, the leaf spring 702 includes a first pressing portion 704 and a second pressing portion 705a. The first pressing portion 704 pressurizes a mirror reflection surface 706 toward a first mirror seating surface 707 provided on the housing 85. On the other hand, the second pressing portion 705a pressurizes a mirror edge portion 708 in a direction of being pressed toward the first mirror seating surface 707 and a second mirror seating surface 709. The reflecting mirror 62 is pressed in two directions by the first pressing portion 704 and the second pressing portion 705a, thereby improving vibration isolating performance of the reflecting mirror 62, and also preventing the reflecting mirror 62 from dropping off when an impact such as a drop impact or vibration is exerted on the reflecting mirror 62.
However, there are the following problems with this structure. That is, the second pressing portion 705a presses the mirror edge portion 708 of the reflecting mirror 62, which is low in strength, and hence shaving, chipping, cracking, and the like may occur in the mirror edge portion 708. In particular, as the optical components such as the reflecting mirror 62 and the lens, there are many products made of a glass material, and in this case, the shaving, chipping, cracking, and the like are liable to occur in the mirror edge portion 708 due to slight contact with other components or the like. When the second pressing portion 705a is brought into contact with the mirror edge portion 708 and powders and fine fragments generated along with the shaving, chipping, cracking, and the like adhere to the mirror, the reflectance of the mirror is degraded, with the result that the light intensity of the light beam to be guided onto the photosensitive drum becomes lower than a desired design light intensity.
As measures to prevent the shaving, chipping, and cracking of the reflecting mirror 62 due to the leaf spring 702, the following structure is proposed. For example, in Japanese Patent Application Laid-Open No. 2010-237537, there is proposed a structure in which a gripping portion configured to grip the leaf spring is provided and deflected by an assembly jig, to insert the reflecting mirror pressing portion to a predetermined position while compressing the pressing portion. In this structure, the assembly jig receives a reaction force generated when the gripping portion is deflected, and thus the leaf spring can be attached without applying a force (hereinafter referred to also as a “stress”) that may cause the shaving, chipping, and cracking in the mirror edge portion of the reflecting mirror. Further, a structure illustrated in FIG. 9A is proposed as a structure configured to prevent the leaf spring from being brought into contact with the mirror edge portion of the reflecting mirror when the leaf spring is attached to a predetermined position. In the structure of FIG. 9A, the portion to be pressed by a second pressing portion 705b corresponding to the second pressing portion 705a of FIG. 8B is changed from the mirror edge portion 708 to a mirror flat surface 710. Note that, elements designated by the other references symbols of FIGS. 8A, 8B, 9A, 9B, and 9C will be described in embodiments of the present invention described later.
In the case of the structure illustrated in FIG. 9A, the stress exerted on the mirror edge portion 708 of the reflecting mirror 62 in the state in which the leaf spring 702 is attached is reduced as compared to that of FIG. 8A. When the leaf spring 702 is to be engaged with the engaging portion 703 of the housing 85, however, the leaf spring 702 moves in contact with the mirror edge portion 708, and hence the shaving, chipping, and cracking may occur in the mirror edge portion 708 by the contact of the leaf spring 702 with the mirror edge portion 708 during the movement of the leaf spring 702. Further, when the leaf spring 702 is attached in the predetermined position, the leaf spring 702 and the mirror edge portion 708 of the reflecting mirror 62 are still in contact with each other. In addition, in the structure of FIG. 9A, the following problem arises at the time of attaching the leaf spring. That is, when the leaf spring 702 is pressed downward as illustrated in FIGS. 9B and 9C so as to be inserted, the leaf spring 702 is pressed in a direction indicated by the arrow 711 in FIG. 9C due to the reaction force exerted by the first pressing portion 704 that presses the mirror reflection surface 706. Further, the leaf spring 702 is significantly inclined as illustrated in FIG. 9C by the engaging portion 703. As a result, the leaf spring 702 is brought into contact with the mirror edge portion 708. Therefore, in order to prevent the shaving, chipping, and cracking of the mirror edge portion 708, it is desired that the leaf spring 702 be prevented from being brought into contact with the mirror edge portion 708 in the process from the start to the end of attaching the leaf spring 702. It is further desired that the leaf spring 702 be prevented from being brought into contact with the mirror edge portion 708 in a state in which the attaching of the leaf spring 702 is finished and thus the leaf spring 702 is attached in the predetermined position. That is, it is desired that the leaf spring 702 be prevented from being brought into contact with the mirror edge portion 708 in the entire process.